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Title: Thin silicon foils produced by epoxy-induced spalling of silicon for high efficiency solar cells

We report on the drastic improvement of the quality of thin silicon foils produced by epoxy-induced spalling. In the past, researchers have proposed to fabricate silicon foils by spalling silicon substrates with different stress-inducing materials to manufacture thin silicon solar cells. However, the reported values of effective minority carrier lifetime of the fabricated foils remained always limited to ∼100 μs or below. In this work, we investigate epoxy-induced exfoliated foils by electron spin resonance to analyze the limiting factors of the minority carrier lifetime. These measurements highlight the presence of disordered dangling bonds and dislocation-like defects generated by the exfoliation process. A solution to remove these defects compatible with the process flow to fabricate solar cells is proposed. After etching off less than 1 μm of material, the lifetime of the foil increases by more than a factor of 4.5, reaching a value of 461 μs. This corresponds to a lower limit of the diffusion length of more than 7 times the foil thickness. Regions with different lifetime correlate well with the roughness of the crack surface which suggests that the lifetime is now limited by the quality of the passivation of rough surfaces. The reported values of the minority carrier lifetime showmore » a potential for high efficiency (>22%) thin silicon solar cells.« less
Authors:
 [1] ;  [2] ; ;  [3] ; ; ; ;  [4] ;  [1] ;  [2] ;  [2]
  1. Department of Electrical Engineering, KU Leuven, Kasteelpark 10, 3001 Leuven (Belgium)
  2. (Belgium)
  3. Department of Physics, KU Leuven, Celestijnenlaan 200 D, 3001 Leuven (Belgium)
  4. imec, Kapeldreef 75, 3001 Leuven (Belgium)
Publication Date:
OSTI Identifier:
22310692
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 17; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CARRIER LIFETIME; CRYSTAL DEFECTS; DIFFUSION LENGTH; DISLOCATIONS; EFFICIENCY; ELECTRON SPIN RESONANCE; EPOXIDES; ETCHING; FOILS; PASSIVATION; ROUGHNESS; SILICON; SILICON SOLAR CELLS; STRESSES; SUBSTRATES; SURFACES; THICKNESS